There is known an image generating system which can generate an image as viewed within a virtual three-dimensional or object space from a given viewpoint. Such a system is very popular since one can experience a so-called virtual reality through it. Now considering a image generating system for playing a gun game, a player (or operator) can enjoy a three-dimensional shooting game by manipulating a gun-shaped controller (or shooting device) to shoot targets such as enemy characters (or objects) and the like which are displayed on a screen.
In order to improve the virtual reality for a player in such an image generating system, it was an important technical problem to produce more real images. It is thus desired that when, for example, a glass plate is broken by impact such as hitting bullet, the broken glass may be more realistically represented.
In the conventional image generating systems, however, an image representing the glass plate broken by the bullet was simply replaced by another previously provided picture representing a broken glass plate. Consequently, the same picture is represented whenever the bullet hits any glass plate. The representation is monotonic and lacks in reality.
According to such a technique, once a glass plate is hit and broken by a first bullet, the image will not change even if the glass plate is subsequently hit by any number of bullets. The representation was insufficient, for example, when it is possible that the glass plate will continuously be hit by many bullets in high-speed continuous shooting.
In the prior art, furthermore, the glass plate will be broken into pieces instantaneously when a bullet hits the glass plate. Thus, it was difficult in the prior art to represent a situation in which the glass plate is gradually being broken.
Where a bullet hits an aggregate object 210 consisting of a plurality of stacked objects as shown in FIG. 19, there are different collapse manners depending on the position of the hit object. For example, if a bullet hits an object 242, it will only collapse. If a bullet hits an object 218, all the objects 222, 224, 226 above the hit object 218 will collapse.
In the conventional image generating systems, however, the previous picture is only replaced by another previously provided picture representing a single manner of collapse even though a bullet hits any of the stacked objects. Therefore, the same manner of collapse is always provided even though a bullet hits any of the stacked objects. This is monotonic and lacks in reality.
According to such a technique, once the aggregate object is hit and collapsed by a first bullet, the image will not change even if the glass plate is subsequently hit by any number of bullets. The representation was insufficient, for example, when it is possible that the aggregate object will continuously be hit by many bullets in high-speed continuous shooting.